Britannia Building Society is setting up a branch in Northampton retail store Beatties.
The society is also setting up two more Britannia Simply Mortgages stores within the next two months.
It is expanding into less conventional branch outlets following the success of a pilot project in Solihull where it set up its first Simply Mortgages store in April.
Simply Mortgages is a retail outlet that sells only mortgages.
The Beatties-based branch in Northampton will sell savings, mortgages and investment products. Customers will be able to use interactive computers to get instant quotes on mortgages. The Britannia branch will have four staff.
Britannia director of retail operations Graham Stow says: "Britannia recognises the importance of offering a modern financial facility which is accessible to the customer."
The building society declines to reveal how much money it is investing in the new stores.
Beatties general manager Neil Jones says: "This initiative from Britannia is ideal for our customers. It offers everything under one roof."